LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 62 (Automatic Transmission Diagnosis - 4L80-E) >> Diagnostic Tests >> DTC P0751: 1-2 Shift Solenoid Valve - Performance >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Turn ignition on, engine off. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records. Using the CLEAR INFO function erases the freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Select TFP SWITCH A/B/C on the scan tool. With the engine operating, apply the brake pedal, and select each transmission range. See TFP MANUAL VALVE POSITION SWITCH LOGIC  table under DESCRIPTION & OPERATION. Does each selected transmission range match the scan tool TFP switch display? If so, go to next step. If not, see DTC P1810: TFP MANUAL VALVE POSITION SWITCH ASSEMBLY - CIRCUIT MALFUNCTION .
  3. Raise and support the drive axle assembly. Start the engine. With the transmission in D4 range, use the scan tool to command 1st, 2nd, 3rd and 4th gears while accelerating the vehicle. The vehicle may need to be road tested. Was a 2-2-3-3 shift pattern only detected? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  4. Inspect the shift solenoid/hydraulic circuit for a 1-2 shift solenoid valve internal malfunction. Inspect the shift solenoid/hydraulic circuits for a stuck 1-2 or 3-4 shift valve. Inspect the shift solenoid/hydraulic circuit for damaged seals on one or both of the shift solenoids. The shift solenoids can cause oil to leak into the 2nd gear clutch pack. See SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING. Did you find and correct the condition? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  5. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Accelerate the vehicle with the throttle angle greater than 7 percent up to 55 MPH.
    • The PCM must see the proper ratio for each commanded gear for greater than one second in D1, D2, D3, and D4.
    • Wait for the TCC lock-up in 4th gear.
    • Select SPECIFIC DTC.
    • Enter DTC P0751.

    Has the test run and passed? If so, system is okay. If not, go to step  1.

scientia non olet · About LEMON Manuals